On May 10, officers raided casino Moebius, located in the Dogenzaka area, and arrested Hiromichi Shibata, the 40-year-old manager, and two other employees for allowing customers to place wagers on baccarat and poker games via 10 personal computers connected to an overseas site.
All three suspects, who have been charged with operating a wagering facility for profit, have reportedly admitted to the allegations.
Police also arrested six male and female customers inside the premises on suspicion of partaking in illegal gambling.
Since opening two years ago, Moebius had collected 200 million yen in revenue.
To monitor customers entering and leaving the casino, a surveillance camera and intercom was installed at the entrance.